Taiwan has fabricated n-type conducting UNCD films by Li-doping at very low temperature of about 570°C by simply using a Li-based substrate material. There is no need to use any heater that usually used for diamond growth processes.
We report monolithic n-type conductivity on low-temperature ( less than 570 °C) grown ultrananocrystalline diamond (UNCD) films by Li-diffusion (about 255 nm) from LiNbO3 substrates. Low resistivity of 1.2 Ω cm with carrier concentration of −2×10^20 cm−3 is obtained on freestanding UNCD films. The films bonded to Cu-tape show very low turn-on field of 4.2 V/μm with emission current density of above 0.3 mA/cm2 at a low applied filed of 10 V/μm. The n-type conductivity of low-temperature Li-diffused UNCD films overwhelms that of the high-temperature ( ≥ 800 °C) nitrogen doped ones and will make a significant impact to diamond-based electronics.